1. Field of the Invention
The present invention relates to an automatic installation involving a prequenching heating, forming, quenching, progressive tempering and finally cooling system for the manufacture in large quantities of pieces which exhibit particular characteristics of strength, flexibility and hardness. This installation is more particularly adapted to the production of circular pieces of small thickness, notably disk springs, saw blades and more particularly spring diaphragms for the automobile industry.
2. Description of Related Art
In recent years, spring diaphragms have been substituted for the traditional maneuvering levers and multiple helical springs placed on the periphery of the automobile vehicle clutching mechanisms. It is known that the spring diaphragm is a steel disk which is deeply serrated in its center and which, when at rest, has a regular conical shape. Prior to its treatment, this piece which is made from spring steel has to be in the annealed state and has a homogeneous metallurgical structure. The treatments to which it is thereafter subjected consist in a heating operation followed by quenching. It may also be necessary to subject the piece to a radially progressive tempering so that the diaphragm spring in the finished state exhibits radially progressive temper and hardness characteristics. The present invention is concerned with providing an automatic installation meeting this requirement on a continuous basis during the whole treatment, namely from the forming stage by hot swaging to the final cooling stage.
An automatic machine which produces clutch diaphragms via a cycle of hot swaging forming and quenching operations is already known. In this respect, one may refer to French Patent No. 1,598,224 which discloses an automatic machine including a heating enclosure containing a conveyor barrel with equidistant radial compartments opening at the periphery of said barrel. The enclosure is imparted with a step by step rotary motion in order to receive on the upstream side of the heating enclosure a cold piece which has to be introduced in an empty compartment of the barrel by charging and discharging means, and on the other hand to deliver to these last means a hot piece from the downstream side of said enclosure. The charging and discharging means operating upstream have means for feeding, one by one, pieces to be treated and stacked inside a feed magazine. Downstream a piece to be formed by hot swaging and quenching means cooperates with gripping and conveyor means conveying each finished piece into a receiving magazine.
Such a machine, while providing pieces swaged and quenched in a uniform manner, does not produce spring diaphragms exhibiting radially progressive temper and hardness characteristics.
In an attempt to solve the problem posed by the production of pieces, such as spring diaphragms presenting the hereabovementioned characteristics of variable temper and thickness, a thermomechanical treatment installation for a series of pieces in which the reheating device, the quenching press, the tempering device and the cooling device are placed immediately one after another, has been recently developed (WO-A-8 605 820). The temperature and duration of each treatment step is controlled in the system according to a preestablished program.
This prior device, however, does not allow controlling in each working station, and continuously, the temperature gradients in the treated pieces so as to obtain pieces having the radially progressive temper and hardness characteristics.
Consequently, the invention provides a device meeting such a requirement.